ABSTRACT
The purpose of this systematic review is to analyze the methodologies, utilized stimulation parameters, and the main cellular outcomes obtained by in vitro studies that apply a light source on tenocyte cultures. Methods: The PubMed, Scopus, and Web of Science databases were searched up to December 9, 2019 for in vitro studies that used light sources on tenocyte cultures. A 13-item checklist was used to assess methodological quality of the studies and the risk of bias was assessed using the Risk of Bias Assessment tool for Non-randomized Studies tool. Results: Six studies were included. Tenocytes from the Achilles tendon were used by 83.3% of the studies, with 16.7% utilizing the deep digital flexor tendon, with cells in passage 2 to 5. Four studies used lasers and the other 2 used light-emitting diode or intense pulsed light, in wavelengths ranges from 530 to 1100 nm. The application of light to tenocytes resulted in positive effects reported by all studies, including an increase in cell proliferation and migration, and higher protein and gene expression of tendon biomarkers. Studies presented a lack of standardization on reporting light stimulation parameters and experimental methodologies, leading to low methodological quality. There was a high risk of selection, performance, detection, and reporting bias. Conclusions: All studies showed positive effects after light stimulation on tenocytes, regardless of the light source used. However, the lack of standardized data on light stimulation parameters, experimental setup, and the studies' main limitations hindered representative conclusions and comparisons amongst studies' main outcomes.
ABSTRACT
Zirconia is becoming reckoned as a promising solution for different applications, in particular those within the dental implant investigation field. It has been proved to successfully overcome important limitations of the commonly used titanium implants. The adhesion of microorganisms to the implants, in particular of bacteria, may govern the success or the failure of a dental implant, as the accumulation of bacteria on the peri-implant bone may rapidly evolve into periodontitis. However, bacterial adhesion on different zirconia architectures is still considerably unknown. Therefore, the adhesion of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa to zirconia surfaces with different finishings was evaluated and compared to a titanium surface. The adhesion interaction between S. aureus and P. aeruginosa was also evaluated using a co-culture since these bacteria are infamous due to their common presence in chronic wound infections. Results showed that different bacterium species possess different properties which influence their propensity to adhere to different roughness levels and architectures. E. coli revealed a higher propensity to adhere to zirconia channelled surfaces (7.15 × 106 CFU/mL), whereas S. aureus and P. aeruginosa adhered more to the titanium control group (1.07 × 105 CFU/mL and 8.43 × 106 CFU/mL, respectively). Moreover, the co-culture denoted significant differences on the adhesion behaviour of bacteria. Despite not having shown an especially better behaviour regarding bacterial adhesion, zirconia surfaces with micro-channels are expected to improve the vascularization around the implants and ultimately enhance osseointegration, thus being a promising solution for dental implants.