Received Date: 24 Jun 2016
Revision Received Date: 25 Jan 2017
Electronic Publication Date: 31 Mar 2017
We thank Mr. Sanya Chiamsuk and Mr. Sorapong Wongnoi, Faculty of Dentistry, Naresuan University, for their technical assistants for SEM. Dr. Jadesada Palasuk and Dr. Potjaman Totiam, Faculty of Dentistry, Naresuan University, for their kindness to edit English manuscript. This study was supported by Thailand Research Fund and Office of the Higher Education Commission (Project Ref. No: MRG5180022).