Acknowledgements
We appreciate the kind suggestions from colleagues at the Department of Orthodontics, Department of Microbiology and Department of Oral Pathology, Faculty of Dentistry, Chulalongkorn University. Moreover, we are grateful to Assoc. Prof. Pichayada Ketmake and Assoc. Prof. Thavatchai Tayjasanant for their valuable support. We also thank Dr. Kevin Tompkins for revising the language in the manuscript.