Effects of Nonthermal Atmospheric Plasma on Adhesive-Dentin Bond Strength: Meta-Analysis

Objectives: The aim of this systematic review and meta-analysis was to evaluate the short and long-term effects of nonthermal atmospheric plasma (NTAP) on adhesive-dentin bond strength.
Methods: MEDLINE, Web of Science and Scopus databases were searched for in vitro studies comparing NTAP treatment to no plasma treatment groups. Online search was performed in March 2019. Inclusion criteria were: non-carious, intact, extracted human or bovine teeth, NTAP treated dentin and short- and/or long-term measurement of adhesive-dentin bond strength. Random effects model was used to summarize the observed treatment effect. Bond strength values were expressed as standardized mean difference (SMD) with 95% confidence interval. Subgroup analyses were performed according to different types of plasma gas.
Results: Fifteen studies fulfilled the inclusion criteria and 13 of those 15 studies were meta-analyzed. The remaining two studies were excluded due to the lack of information and no response from authors.
Evaluating short-term effects of NTAP on adhesive-dentin bond strength, based on all 13 studies with a total of 2052 specimens (sticks), the results showed statistically significant difference between NTAP and control group in favor of NTAP (SMD 1.87; 95% CI [1.23, 2.50]; p<0.0001). Subgroup analysis revealed a significant effect in studies that used He (SMD 5.11; p<0.0001) but not for studies that used Ar (SMD 0.11; p=0.56).
In the long-term, NTAP presented a positive overall effect on assessing the outcome (SMD 3.76; 95% CI [2.84, 4.68]; p<0.0001) based on pooled results from 10 studies with a total of 1660 specimens. Subgroup analysis confirmed the effect in studies that used He gas (SMD 15.1; p<0.0001 ).
Conclusions: Dentin treatment using NTAP significantly increased short- and long-term adhesive-dentin bond strength. The main proposed mechanism of NTAP-dentin interaction was improved hydrophilicity of the dentin surface through changes in polarity, leading to improved adhesive distribution.