Evaluation of viability of periodontal ligament cells using propolis, coconut water, aleo vera, and soy milk: An In vitro comparative Study oleh Sandeep Sharma, Prabu Mahin Syed Ismail, Muhammed Atif Saleem Agwan, Anshul Chandra, Amol Jain, Noura Alessa, Swati Srivastava