[1] Kuwait Univ, Dept Surg Sci, Fac Dent, Hlth Sci Ctr, Kuwait, Kuwait
[2] Rigshosp, Copenhagen Univ Hosp, Dept Oral & Maxillofacial Surg, Ctr Rare Oral Dis, Copenhagen, Denmark
[3] Leeds Dent Inst, Paedriat Dent, Leeds, W Yorkshire, England
[4] Bradford Dist Care Trust Salaried Dent Serv, Leeds, W Yorkshire, England
[5] Univ Adelaide, Sch Dent, Fac Hlth Sci, Endodontol, Adelaide, SA, Australia
[6] Univ Penn, Sch Dent, Dept Endodont, Philadelphia, PA 19104 USA
[7] Hennepin Cty Med Ctr, Dept Dent, Minneapolis, MN 55415 USA
[8] Univ Minnesota, Sch Dent, Minneapolis, MN 55455 USA
[9] Hosp Sick Children, Toronto, ON, Canada
[10] Univ Toronto, Toronto, ON, Canada
[11] UNC Sch Dent, Dept Endodont, Chapel Hill, NC USA
[12] Univ Valparaiso, Dept Pediat Dent, Fac Dent, Valparaiso, Chile
[13] Univ Maryland, Sch Dent, Dept Endodont, Baltimore, MD 21201 USA
[14] Karolinska Univ Hosp, Div Pediat, Dept Clin Sci Intervent & Technol, Stockholm, Sweden
[15] Univ Queensland, Brisbane, Qld, Australia