[1] Univ Calif, Inst Expt Biol, Div Dent Med, Berkeley, CA USA
[2] Univ Calif, George Williams Hooper Fdn Med Res, Berkeley, CA USA
[3] Univ Calif, George Williams Hooper Fdn Med Res, San Francisco, CA USA
[4] Univ Calif, Inst Expt Biol, Div Dent Med, San Francisco, CA USA