^pof;
Periodontology,;
School;
of;
Life;
Dentistry;
at;
Niigata,;
Nippon;
Dental;
University,;
Niigata;
951-1500,;
Japan;
^pof;
Dental;
Materials,;
School;
of;
Life;
Dentistry;
at;
Niigata,;
Nippon;
Dental;
University,;
Niigata;
951-1500,;
Japan;