Funding for this research was provided by:
Rural development administration (PJ01313902)
Article History
Received: 13 September 2018
Accepted: 8 October 2018
First Online: 25 November 2018
Ethics approval and consent to participate
: This retrospective study was approved by the Institutional Review Board of Gangneung-Wonju National University Dental Hospital (IRB 2018-004).
: Not applicable.
: The authors declare that they have no competing interests.
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